“Study of consistency and stability of the flattening filter free beams in elekta versa hd”

The purpose of the study was to evaluate the consistency and stability of the 6FFF, and 10FFF Flattening Filter Free (FFF) beams in terms of beam output, beam quality, symmetry, degree of unflatness and penumbra in Elekta Versa HD machine for a period of two years. Output constancy and beam quality index were measured using farmer type ion chamber in the water phantom in standard measurement conditions. To study the characteristics of the beam profiles, beam data measurements were performed in Radiation Field Analyser (RFA) using 0.125cc pinpoint chamber. All the scanned PDD and profile measurements were analysed using PTW's MEPHYSTO mc2 navigation software. Output constancy showed a mean difference of -0.35%±0.53SD and 0.46%±0.58SD for 6FFF and 10FFF respectively when compared with commissioning data. The maximum deviation was observed in the beam quality index were -1.35% for the 6FFF beam. Profile measurements showed that the Beam symmetry, degree of unflatness and penumbra were met the AERB task group recommendations. This study revealed that routine quality assurance has an excellent agreement with baseline data. Beam constancy and profile stability of the machine was very robust and well within the limit for two years.